1. Field of the Invention
This invention relates to a printing apparatus and, in particular, to a printing apparatus which receives printing data from a multiplicity of devices for printing.
2. Description of the Prior Art
FIG. 1 shows the operating condition of a conventional printing apparatus which prints the print (data from a multiplicity of host devices. In the same figure, the print control section receives a print request from three types of host devices A, B, C and controls actual printing at the print operation section. The hatched portion in the print control section indicates that it carries out processing for converting the print request from each host device into a form by which the print request can be made to the print operation section, while the hatched portion in the print operation section indicates that the section is printing on paper.
Conventionally, the printing apparatus which receives printing data from a multiplicity of host devices for printing returns RECEPTION DISABLED (hereinafter called "BUSY") white the print request from one host device is being processed because it is under operation for the print request from another host device. For example, in FIG. 1, when print requests from the host devices B, C are inputted while the host device A makes a print request to the print control section and before the print is finished, BUSY is outputted and the print requests of the host devices B, C cannot be received. Therefore, the host devices B, C which received BUSY must wait until the print process of the host device A is completely finished and must make a new print request. This series of operations not only lowers the throughput of the printing apparatus but also processing of BUSY monitoring of host devices has created a significant burden.
Because any print request from another host device is riot accepted while a print request from one host device is being processed, even when the print operation section is ready for printing, if the paper of the size requested by the print request currently under processing is riot set, even if the paper of the size requested by the print request made by another host device is set, the print request of this other host device is not processed unless the paper of the size requested by the print request under processing is set.
The series of operations and problems as described above result from the control method of the print request in the conventional printing apparatus. FIG. 2 shows a conventional control system of the print request. In the figure, the print request for each page is stored successively in a specified region. The progress of each processing is controlled by the paper discharge pointer, extension pointer, print pointer, BMM (bit map memory) acquirement pointer, and next print request pointer. In this control method, processing is only possible in order of print requests received. Therefore, it is impossible to stop a print request only from one host device or to hold a print request from a host device when the paper of the size requested by the print request is not available and to process the next print request. Because a control system for processing print requests of a multiplicity of host devices in parallel is not adopted in this way, the conventional printing apparatus is designed to reject the print requests of other host devices while a print request from one host device is being processed. This has resulted in low throughput of the printing apparatus and created a problem in that print requests of all the host devices cannot be received once any trouble occurs in the print request from one host device.
In the printing apparatus with a multiplicity of paper feed inlets and discharge outlets, when a discharge outlet is specified, conventionally, one paper feed inlet and discharge outlet are specified from among these paper feed inlets and discharge outlets by the command from host devices or the input using the operation panel on the printing apparatus side. In this type of specifying method, even if the paper feed inlet other than that specified is available in the printing apparatus with a multiplicity of paper feed inlets, if the specified paper feed inlet is unserviceable, ERROR is outputted and the printing operation cannot be begun. To solve this problem, application from the host device should be modified so that a multiplicity of paper feed inlets are allowed to be specified, but there is a problem that modification of application is difficult.
Now, the character font cash control is carried out word by word or host code by host code for two-byte based characters. in the conventional technology. When the cash registration number exceeds the limit, the cashed character font patterns are deleted successively in order of older registration time or larger size of font pattern data, or lower ranking of priority given to each font pattern.
Under this kind of conventional character font cash control method, it is difficult to control the character font pattern with the same code but a different font or character size, and it is also difficult to control the different code system. If the cashed character font patterns are deleted successively in order of older registration time or larger size of data, it is impossible to effectively use the cashed font patterns. It is possible to effectively utilize the cashed font patterns if priority is given to the patterns, but processing associated with it is complicated and an expected high speed may not be achieved in cash processing. If the deletion timing is controlled by the number of registration, deletion must be performed even when there is a space in memory, not resulting in an effective use of memory.